The Czech Socialist Republic (Česká socialistická republika in Czech; abbreviated ČSR) was the official name of that part of Czechoslovakia that is the Czech Republic today. The name was used from 1 January 1969 to March 1990.

After the occupation of Czechoslovakia in 1968, liberalisation reforms were stopped and reverted. The only exception was the federalization of the country. The former centralist state Czechoslovakia was divided in two parts: the Czech Socialist Republic and the Slovak Socialist Republic by the Constitutional Law of Federation of 28 October 1968, which went into effect on 1 January 1969. New national parliaments (the Czech National Council and the Slovak National Council) were created and the traditional parliament of Czechoslovakia was renamed the "Federal Assembly" and was divided in two chambers: the House of the people (cz:Sněmovna lidu / sk:Snemovňa ľudu) and the House of Nations (cz:Sněmovna národů / sk:Snemovňa národov). Very complicated rules of voting were put in effect.

After the fall of socialism in Czechoslovakia, the word "socialist" was dropped from the names of the two republics, i.e. the Czech Socialist Republic was renamed the Czech Republic (though it was still a part of Czechoslovakia).

The complicated system of parliamentary voting (there were de facto 5 different bodies each having right of veto) was kept after the fall of socialism, complicating and delaying political decisions during radical changes in the economy.